Obstacles to inspiring people to "be the change"

Gandhi's expression "Be the change you want to see in the world" gets quoted quite a bit.  But to what end?

It's one thing to consider embracing activism and avoiding burn-out for those who are already jazzed about getting involved in advocacy, but most people don’t constantly write letters or go to rallies. They don’t focus their frustration. There dozens of ribbons and hundred of groups and thousands of little causes mingling with the bigger ones. Like something on Facebook, retweet something on Twitter and you have been “active”. 

I wrote one email to an elected official this year. I clicked to “sign” a few online petitions. That’s it. And I am fairly well-informed. I know the stakes. So why don't more people turn their concerns into action?